Process for accreting molten copper on a moving core member

ABSTRACT

THIS PATENT RELATES TO AN IMOROVEMENT IN THE CONTINUOUS CASTING DIP FORMING PROCESS. IN THE DIP FORMING PROCESS FOR MAKING WIRE ROD A CORE MEMBER IS PASSED UPWARDLY THROUGH A CRUCIBLE CONTAINING A MOLTENT METAL. THE CRUCIBLE CONTAINS A NOZZLE OR BUSHING THROUGH WHICH THE CORE MEM-   BER PASSES AT A RELATIVELY HIGH RATE. CONSTRUCTION MATERIALS FOR THIS NOZZLE OR BUSHING ELEMENT ARE CRITICAL IN OBTAINING HIGH QUALITY WIRE ROD.

9, 1973 D. A. CORRIGAN ETAL 3,709,722

PROCESS FOR ACCRETING MOLTEN COPPER ON A MOVING COBB MEMBER Original Filed April 6. 1970 2 Sheets-Sheet 1 HGUREI 2 Sheets-Shee t 2 .1 I "a." w u FIGURE 25 Jan. 9, 1973 CORRIGAN ETAL PROCESS FOR ACCRETING MOLTEN COPPER ON A MOVING CORE MEMBER Original Filed April 6, 1970 FIGURE 2A FIGURE 2C 3,709,722 Patented Jan. 9, 1973 3,709,722 PROCESS FOR ACCRETING MOLTEN COPPER ON A MOVING CORE MEMBER Donald A. Corrigan, Marblehead, and Italo S. Servi and Chih-Chung Wang, Lexington, Mass., assignors to Kennecott Copper Corporation, New York, N.Y. Original application Apr. 6, 1970, Ser. No. 25,770, now Patent No. 3,610,204. Divided and this application Apr. 7, 1971, Ser- No. 132,227

Int. Cl. C23c N US. Cl. 117-114 R 2 Claims ABSTRACT OF THE DISCLOSURE This patent relates to an improvement in the continuous casting dip forming process. In the dip forming process for making wire rod a core member is passed upwardly through a crucible containing a molten metal. The crucible contains a nozzle or bushing through which the core member passes at a relatively high rate. Construction materials for this nozzle or bushing element are critical in obtaining high quality wire rod.

This is a division of application Ser. No. 25,770 filed Apr. 6, 1970 and now Pat. No. 3,610,204.

BACKGROUND OF THE INVENTION The dip-forming process, such as used in continuous casting of metal, is now well known in the art. According to this process, an elongated body or core material such as a metal rod is typically pretreated by passing it through a straightener, a surface cleaning apparatus and a shaving die which also serves as a vacuum seal for a vacuum entrance chamber positioned below or at the bottom of a crucible containing a bath of molten material. The continuous elongated core or body is passed upwardly through the molten bath, which bath may have the same chemical composition as that of the core or a different composition. The molten material in the crucible accretes or deposits upon the outer surface of the core thereby increasing its cross sectional area appreciably, After emerging from the crucible the resulting casting member is cooled as by a water spray from one or more jet nozzles at least sufficiently so that the cast member may be rolled or worked. From there the cast member may be passed through a suitable roller mechanism where it is reduced in crosssectional area and then passed to a suitable receiving means such as a take-up reel.

The dip-forming process briefly described above is fully set out in one or more of the following patents:

Patent No. Inventor Issue date 3,008,201 R. P. Carreker, Jr 11/14/61 3,060,053... R.tP.lCarreker, Jr. /23/62 e is.

3,060,054 J. A. Russell et al 10/23/62 3,060,055 H. H. Blxler 10/23/62 3, B- B. Scott 10/23/62 3,235,960.- R P Carreker,Jr 2/22/66 3,406,186 R. P. Carreker, Jr. 9/9/69 use of a molybdenum bushing or nozzle through which the core material passed into the molten copper bath.

Two alternate causes of molybdenum inclusion in the copper rod appear to contribute to the problem. Mechanical removal of molybdenum particles from the bushing or nozzle may be due to spalling, welding, and/or gelling. In combination with the mechanical removal, or by itself, there may be intergranular attack of molybdenum by molten copper and/or atmosphere in the molten metal crucible. It is theorized that the molybdenum particles embedded in the core material as it passes through the molybdenum bushing are those particles dislodged from the molybdenum bushing after the grain boundary is weakened by a combination of impurities and high temperatures. Certain impurities in the molten copper probably change the Wetting characteristic at the molybdenum grain boundaries and the grain boundaries thus become weakened and particles of molybdenum become susceptible of mechanical removal by the core passing through the bushing. The fact that molybdenum is not insoluble in liquid copper may also contribute to the diificuity experienced.

Three patents cited above, Pats. 3,008,201; 3,325,960 and 3,466,186, refer to the use of a refractory metal bushing or nozzle in the dip forming system. In these cited patents the only refractory metal specifically named is molybdenum. Our investigation shows that two of the three refractory metals generally commercially available, i.e. molybdenum and tantalum, are not suitable for use in the dip forming system. The third commercially available refractory metal, tungsten, according to our investigation, finds marginal use in the dip forming system but is not as effective as other metals such as rhenium or rhenium based alloys. Thus it is clear that the teaching in the cited patents cannot be relied upon by one skilled in the art.

SUMMARY AND OBJECTS The invention therefore relates to a method for accreting molten material, i.e. copper, on a continuously. moving rod wherein the rod passes through an entrance bushing whose physical characteristics are such that no material will be removed from the bushing and deposited on the moving rod to cause inclusions in the accreted rod or the wire products made therefrom. The chief object of the present invention is to provide an improved method and process for accreting molten material on a moving rod to form a rod having greater thickness and being substantially uniform in character and free of detrimental inclusions, welded particles, tears, scrapes, gouges, and scratches experienced in the prior art process. Still another object of the invention is to provide an entrance bushing to the molten metal crucible having physical properties that will not result in mechanical removal of particles from the bushing due to spalling, galling, welding, and/or tearing.

DESCRIPTION OF THE INVENTION The attached drawings illustrate a preferred embodiment of the invention.

FIG. I is a schematic flow diagram of the elements required to practice a method of accreting molten material on a moving member.

FIGS. 2A, 2B and 2C are sectional views of a portion of the crucible illustrating the area through which the core member is introduced into the crucible and illustrating three types of bushings or nozzles.

As shown in FIG. 1, which is a schematic representation of the overall dip-forming process, an elongated body 1 of a length of material in the solid state having a first cross sectional configuration and area is continuously withdrawn from a storage means 2 such as a reel or the like and is guided by an appropriate means such as a pulley 3 through preliminary treatment apparatus which may consist of a conventional straightener 4, a conventional surface cleaning apparatus 5, for example an electrolytic bath, and a rinsing or washing bath 6. The straightened, cleaned and Wet body 1 is guided by means 7 into and through an elongated or tubular conduit 8 comprising a drying means 9 which may be supplied with a neutral atmosphere from a source 10, conventional power driven feeder rolls 11 which frictionally engage and drive body 1 into a vacuum entrance chamber 12 provided with a vacuum source 13, which permits the body to pass therethrough while subject to vacuum but which prevents the passage of atmosphere therewith, and an entrance port 14 provided in the bottom of a crucible 15. The body 1 is then passed through a bath of molten material contained in crucible 15, the bath suitably but not necessarily having the same chemical composition as body 1.

Molten material in crucible 15 accretes or deposits and solidifies upon the outer surface of the body 1 increasing its cross-sectiona1 area appreciably into a body 16 which may be of substantially homogeneous composition. After emerging from crucible 15, the body 16 may be subjected to water sprays from jet nozzles 29 and thereby cooled and then passed between sizing apparatus, such as a pair of sizing rolls 17 which function to remove or correct minor surface irregularities. The body 16 is then guided by means of a cooling duct or conveyor 18 to any suitable receiving means such as a reel 19 where it may be allowed to accumulate. From the reel or receiving means 19 the body is passed through conventional reducing apparatus 20 such as wire drawing apparatus or rolling equipment Where the body 16 is reduced to a body 1' having any desired reduced cross-sectional area.

Body 1' may be allowed to accumulate at a storage means 21 such as a reel or the like. When a sufficient.

length of body 1' has accumulated in the storage means 21, body 1' may be cut and the remainder of the body diverted to storage means 22 as product 23. Product 23, as indicated by arrow 24, may be substantially continuously fed to other fabricating apparatus or may be packaged at this point as a final product.

The portions of the body 1 stored at 21 may be used to replenish body 1 in storage means 2 and permit continuous operation of the apparatus.

Since body 1 is continuously passed through the crucible 15 molten material is continuously removed from the crucible. The depth of the molten material in the crucible should be preferably maintained at a substantially constant depth and this may be continually accomplished by providing a melting apparatus such as furnace 25. Material having the appropriate composition is melted in furnace 25 and permitted to flow into the crucible through a conduit 26, a regulating valve 27 and a heating launder or conduit 28 into the bath contained in the crucible 15.

Referring now to FIGS. 2A, 2B and 2C, there is shown various designs of the entrance bushing or nozzle through which the core or wire rod passes into the molten metal bath. In FIG. 2A there is shown a tube 30 defining an evacuated passage through which the core rod 1 passes into the crucible 31. Between the crucible 31 and the crucible liner 32 there is a nozzle 33 through which the core rod 1 passes into the molten bath 34. The nozzle 33 is a cylindrical member to be constructed from the materials as herein described.

In FIG. 213 there is shown another nozzle and entrance port design. The entrance port comprises a centrally apertured cylindrical bushing element 50 of a thermally conductive material such as copper having a flange 51 at one end and a reduced cylindrical extension 52 at its other end. The centrally disposed aperture at the outer end of extension 52 is enlarged and internally threaded as shown at 53. A thin wall tubular element or bushing 54 constructed of the materials as described in this application is provided with a threaded collar 55 at about its midpoint and is threadedly secured to extension 52 with a portion of its length, forming a liner for extension 52 as shown. A substantially cylindrical bushing 56 of a ceramic material such as fired alumina or the like, is provided with a central aperture which receives extension 52 and that portion of tubular element 54 which extends beyond the terminal portion of extension 52. A bottom wall of crucible 60 is provided with an aperture 57 within which is secured a substantially cylindrical centrally apertured bushing 58 of a refractory material such as graphite which retains within its aperture ceramic bushing 56 as shown. Cooling means such as coil 59 through which coolant may be circulated is in heat exchange relationship with element 50 as shown and serves to extract heat from element 50 and tubular element 54.

In operation, body 1 passes through the central aperture of element 50 and through the tubular member or element 54 and emerges in the bath of molten material contained in crucible 60. The internal dimensions and configurations of tubular member 54 is such that body 1 may freely pass thcrethrough but molten material may not leak downwardly along body 1..

FIG. 2C illustrates yet another design for the entrance port to the molten metal crucible. Crucible liner 62 containing molten metal 68 is enclosed in a crucible 61. Tube 65, adapted to be evacuated, is connected to a vacuum source through tube 67. As rod 1 passes through the opening of tube 65 and is introduced into nozzle 69 suitable clearance space 66 is provided between rod 1 and the nozzle surface. At the discharge end 63 of nozzle 69 hydraulic pressure of the molten metal in the crucible liner 62 combined with the vacuum in the opening brings the solidified material into the clearance 66. Continuous solidification of molten material at discharge end 63 of the nozzle substantially prevents molten material flowing into nozzle to impede the successful operation of this continuous accretion.

Having discovered the major cause for the wire breakage in copper wire made from the dip formed rod, the applicants devised an accelerated test to determine the characteristics of materials that would meet the requirements of not spalling, galling, welding or tearing when a rod or core member was passed through a member made from the test materials at a speed equal to or greater than that used in the copper dip forming process. A series of simulated tests were carried out by rotating a copper surface in contact with the surface of a test material, at such a speed that the outer portion of the copper surface traveled at least about 200 feet per minute which is the approximate velocity at which the core or wire rod travels during a typical dip forming operation. The experiments were carried out using a 7 diameter copper wire rod actually produced by the dip forming process. A cross section of this copper rod was polished and the rod was inserted in a drill press. The candidate test materials were mounted in plastic and polished. A 200 gram force was applied between the copper wire rod and the candidate material surfaces. A drill press was rotated at about 3600 r.p.m. for 10 minutes. After the test the two meeting surfaces, that is the surface of the copper rod and the candidate test materials, were observed with a micro scope. The copper rod surfaces were also analyzed by the electron microprobe for the major elements contained in the test material.

The first test was carried out using molybdenum as test material. After the test, the molybdenum surface was severely scored, and these grooves were partially filled with copper mixed with molybdenum particles. The copper surface was severely roughened and several molybdenum inclusions were clearly visible. These inclusions were positively identified by the electron microprobe as pure molybdenum. This test confirmed the earlier findings of molybdenum inclusion in the broken wire.

Other tests were carried out using tantalum, tungsten, tungsten-25% rheniurn, molybdenum-50% rheniurn, soft rhenium, hard rhenium, alumina, and sintered tungsten carbide as candidate materials with the following results:

relatively expensive. Alloying rhenium with molybdenum indicated that a suitable rhenium-molybdenum alloy for nozzle material contains at least 50% rhenium. Although TABLE I I C (m, f tungsten alone 1s a reasonably satisfactory bushing rna- 5 terial it may be advantageously alloyed with rhenium. Test material Co er surface Test material surface Any tungsten-rhenium alloy may be used within the scope Molybdenum, 50% Amwscmtchcs, dark A {ewscratches anda of this invention. For economic considerations tungstenrhenium. material deposited on m a ig n f rk rhenium alloys containing about 25% or less rhenium ififigggfg eposited are preferred. it appears that tungsten carbide and alumina materbiall contained may be acceptable construction materials except that their gggg ff well known low impact resistance and thermal shock Soft rhenlumflmu Ai'evgsclrlatghtkiis, no sul'tfloescgfilgl tg n d sensitivity may cause these materials to shatter in service. gg gi f fifi f 23? 5 5 252 What we claim as new and desire to secure by Letters Hard rhenium somebtafiiislhlkrlig, no Excellent. surface. Patent 0f the Umtecl States 15: em e B( I emum.

Tungsten Several scratches, severe Very few scratches, 15 In a method for dccrenng molten copper on zlefoirmalglotn, some lightnstafln, ognerwlse tmuously movm g core rod, the steps which consist in passjggg g gg ensurdm' ing the core rod from the atmosphere into an evacuated Tungsten, 25% Some tarnishing, no Excellent surface. passage, introducing the moving rod from the passage rhenium. embedded rhenium into a noz l 1 t d m I f normngstem z e oca e 1n e ower portion 0 a crucible Tantalum setversly erodedfiliut no Copprsr welditl ltot] containing molten copper, passing the moving core rod ll 31 UY'QC., ll 3 sum $2 2 mes through the molten copper causing accretion of molten Sintered tungsten Some tarnishing, no Excellent surface copper on the mOVlIlg rod and passing the rod from the carbide. embedded tungsten integrity. 4

Cohan, crucible; the improvement whet em the moving rod 18 A umina VBXY 111139 tar is i g, E fi t introduced into a nozzle gonslructgd from a hard nonotherwise excellent surface.

TABLE II Test materials Molybdenum, Tungsten, %rheniu1n 25%rheniun1 Tungsten Molybdenum Tantalum Tungsten Rhenlurn alloy alloy carbide Alumina Relative hardness Soft Soft Hard.---- Hard.-." so r nfiwhere Hard. Very hard.-. Very hard.

8 W601] hard and soft.

Stalulgijlty of test materlalln 1,400 p.p.m. 250 p.p.m... 1 p.p.n1 1 p.p.rn. Unknown..- Unknown Unknown"..- Unknown.

1q copper.

Observed cold welding Yes Yes N0 No N0 N0 N0 No Test material known to be Yes Yes N0 N0 N0 Yes Yes.

prone to spelling.

Test rod surface 1 Very poor ery poor. Good.... Excellent. Excellent-.. Excellent Excellent- Excellent.

Test rod surfaces contolns No No N0 No N0 No No.

test material particles. Testmaterialuseful asbush- Yes Yes YES Yes Probably Probably no.

ing material.

1 Wlodek, S. T., and Wulfi, J., Trans. AIME 218 (1960) 716.

1 Visual and microscopic observation of surfaces of test materials and copper rod.

Table II lists some known physical properties and observed characteristics of the test materials.

As can be observed from a study of Table II the refractory metals, molybdenum and tantalum, would not be satisfactory materials for construction of the nozzle or bushing.

Several observations can be made from Table II with regard to the physical characteristics of materials from which entrance bushings or nozzles may be made. Relatively hard materials, i.e., tungsten, rhenium, and rhenium based alloys should be used to make the nozzles rather than the relatively soft refractory metalsmolybdenum and tantalum. Solubility of the nozzle construction material in molten copper should be less than approximately 250 parts per million. Cold welding should not occur between the core rod and the bushing or nozzle construction material. The core rod surface should be relatively unaffected by its unavoidable contact with the interior walls of the bushing while moving at speeds of about 200 or more feet per minute.

From our tests and observations rhenium would be the most ideal material for the bushing. However it is cold welding metal selected from rhenium, rhenium based alloys, tungsten and tungsten-rhenium alloys.

2. The method of claim 1 wherein the nozzle is constructed from a metal selected from a rheninm-molybdenum alloy containing at least 50% rhenium, and a tungsten-rhenium alloy containing at least tungsten.

References Cited ALFRED L. LEAVI'IT, Primary Examiner J. R. BATTEN, 1a., Assistant Examiner US. Cl. X.R. 

